My Albin 27 came with black bottom paint, ablative. I over coated (is that a word?) with 3 coats of WM blue ablative. Now I sold that boat this past Oct. One full year after painting the bottom. I bet the new owner will not have to paint the bottom for at least 3 years, maybe more. He won't have to paint until he sees the black coming through the blue.
Now that you read all this bottom paint BS, here's the point. The boat is in the water, you won't see the painted bottom IMHO the bottom paint color is not a big issue. If you trailer your boat you do not have to paint, the boat won't be in the water long enough for growth to become a problem.
I'll say it again, if you trailer your boat, you DO NOT have to paint the bottom. Bottom painting is not a mandatory right of boat owership passage. Having painted a 30' sailboat twice, and a Albin 27 once x 3, it is a chore I can live without, and so can you, unless you store your boat in the water. If that's the case have at it, use ablative 3 coats get 3 plus years out of your labor.